Fabrication and Characterization of Unidirectional Fiberglass Mat/CSM Hybrid Composites Using a Vacuum Infusion Process

In this paper, a combination of unidirectional fiberglass mat and chopped strand mat layers in isophthalic resin is used to fabricate hybrid composites. The vacuum infusion process is applied for composite fabrication. The effects of the fiber orientation of the unidirectional plies and the addition of the chopped strand mat plies on the physical and mechanical properties of the developed hybrid composites are investigated. Three different laminates are developed with seven and fifteen laminae. Physical properties including fiber density and weight fraction are evaluated. A modified rule of mixture is proposed to evaluate the theoretical densities of the hybrid laminates, which has an excellent agreement with experimental densities. The hybrid laminates exhibit higher densities and lower void content than the unidirectional laminates. The mechanical properties are determined using tensile and three-point bending tests. The hybrid laminate with seven plies has the best properties in all fiber orientations and is the optimum laminate. Increasing the fiber orientation has drastically reduced the tensile and flexural strengths of the unidirectional composite. However, the variation of the strengths with the fiber orientation is not significant in the hybrid laminates. By increasing the laminate thickness, the tensile and flexural strengths have not changed significantly. However, the maximum flexural strain has increased with laminate thickness. The hybrid laminate with fifteen plies has considerable strain under bending and is suitable for applications where high ductility is required.